1. Field of the Invention
This invention relates to apparatus for preventing flooding as a result of leakage from a water heater located in a building, and more particularly concerns apparatus for detecting such leakage and shutting off water flow to the leaking water heater.
2. Description of the Prior Art
Water heaters, whether in residential or commercial buildings, are susceptible to failure in a manner wherein the water within the heater and water entering the heater will leak uncontrollably onto the underlying floor. Such flooding could cause extensive damage to the building and its contents.
Systems have earlier been described for sensing a leak in a plumbing system, and automatically turning off the water feeding the plumbing system. One type of such detection and control system employs flow monitoring sensors intended to discriminate between normal water flow and abnormal flows attributable to leaks. Such systems monitor either instantaneous flow or flows over a timed period, and send an electrical control signal to a shut-off valve. Such systems are disclosed, for example, in U.S. Pat. Nos. 4,589,435; 4,705,060; 5,000,224; 5,038,802; 5,056,554; 5,086,806 and elsewhere. Water shut-off systems of the aforesaid nature usually involve expensive computerized equipment and generally require specialized programming for proper installation.
In still other flood control systems, as disclosed in U.S.  Pat. No. 4,324,268 and 5,240,022, sensors are disposed at floor level for detecting the presence of water, said sensors employing the water to complete an electrical circuit between two closely spaced electrodes. Such systems are unfortunately activated by the small amounts of water employed in the wet-mopping of floors, or small amounts of accidentally spilled water.
In yet another type of plumbing flood control system, as disclosed in U.S. Pat. No. 6,523,562, a float-activated electrical switch positioned in a water-accumulating chamber is employed to control an electrically actuated valve. All the aforesaid plumbing flood control systems require a dependable source of electricity, and further permit the possibility of denial of water service to essential but sporadically operating systems such as fire extinguishing systems, lawn watering and cooling systems.
U.S. Pat. No. 6,543,471 describes a spring operated mechanism which, in response to the rising of a float device within a collecting pan beneath a water heater, causes a trigger mechanism to close a valve that supplies water to said heater. However, said spring mechanism requires a tether line that extends to an operating lever of the valve, and such arrangement compromises the reliability of the mechanism. Also, the trigger mechanism is subject to malfunction due to effects of corrosion or dirt accumulation.
It is accordingly an object of the present invention to provide apparatus of improved reliability for automatically preventing flooding that might be produced by a faulty water heater. 
It is a further object of this invention to provide apparatus as in the foregoing object which does not require a source of electricity.
It is another object of the present invention to provide apparatus of the aforesaid nature which is easily installable and is of durable construction amenable to low cost manufacture.
These objects and other objects and advantages of the invention will be apparent from the following description.